1. Stellenbosch University; Faculty of Medicine and Health Sciences; Cape Town South Africa
2. Stellenbosch University; Centre for Evidence-based Health Care, Faculty of Medicine and Health Sciences; PO Box 19063 Tygerberg Cape Town South Africa 7505
3. South African Medical Research Council; South African Cochrane Centre; PO Box 19070 Tygerberg Cape Town South Africa 7505
4. University of Cape Town; School of Public Health and Family Medicine; Rondebosch Cape Town South Africa 7700
5. Stellenbosch University; Department of Paediatrics and Child Health , Faculty of Medicine and Health Sciences; Tygerberg South Africa
6. University of Bern; Institute of Social and Preventive Medicine (ISPM); Finkenhubelweg 11 Bern Switzerland CH-3012